Composition control of CSVPE HgCdTe

Abstract

Method for growing HgCdTe (15) upon a CdTe substrate (5) using a HgTe source (3) and close-spaced vapor phase epitaxy (CSVPE). A processing temperature T of between 520° C. and 625° C. is employed over a processing time t of between approximately 1/4 and 4 hours. The thickness A of the grown HgCdTe (15) is a linear function of processing time t. The mole fraction x of cadmium in the HgCdTe (15) is a linear function of temperature T and an exponential function of the mole fraction y of mercury in the source (3). The lower the relative amount of mercury in the source (3), the greater the relative amount of mercury in the end product (15), and vice versa. Any crystal plane and any axial orientation of the CdTe substrate (5) can be used without affecting the rate of growth of the HgCdTe (15), the single crystal nature of the HgCdTe (15), or the mirror-like finish of its surface. At least 90% of the transition between the CdTe substrate (5) and the grown HgCdTe layer (15) occurs within the first 20% of the HgCdTe layer (15); for distances greater than this away from the substrate (5), the HgCdTe (15) exhibits a substantially uniform x.

What is claimed is: 
     
       1. A layer of HgCdTe epitaxially grown on a CdTe substrate using the closed-space vapor space epitaxy method, wherein the thickness of the grown HgCdTe layer is between 3 microns and 24 microns, and the mole fraction of cadmium in the HgCdTe which is situated greater than 20% of the HgCdTe layer thickness away from the CdTe substrate varies by no more than 10% as a function of distance from the substrate; wherein said layer is formed by a process in which a HgTe source material and CdTe substrate are spaced apart from each other by a distance of between 0.1 mm and 10 mm; and   the source material and the substrate are then heated together at a constant processing temperature of between 520° C. and 625° C. for a fixed processing time of between 1/4 hour and 4 hours.   
     
     
       2. The layer of claim 1 in which the source material is Hg y  Te, where 0.8≦y≦1.